1. Field of the Invention
The present invention relates to a network switching system, and more particularly to a network switching system applicable to a wireless or mobile network system.
2. Description of the Background Art
In a wireless network system, for example, access control between plural wireless network devices is managed by a wireless access device, called as access point-device. In general, the access point device is disposed on a wired network for connection to an external network or to other access point devices. Hence, there was raised a problem that no access point devices may be provided under the situation, for example, where a wired network cannot-be laid, with the result that it is not possible to construct a wireless network connectable to an external network.
For overcoming this inconvenience, a wireless mesh network has now been proposed, in which a plurality of access point devices are arranged in the form of meshes, and are interconnected by wireless channels with the connections implemented by wired circuits minimized so as to attain a broader service area connectable to the network, as taught by Japanese patent laid-open publication No. 2005-184522.
In a wireless network, in order to set up both-way transmission between plural wireless network devices, it is necessary to determine a transmission path between the devices. The conventional methods of determining transmission paths between wireless network devices include, for example, ones based upon a proactive OLSR (Optimized Link State Routing) protocol or a reactive AODV (Ad hoc On-demand Distance Vector) protocol, which are respectively taught by Toshio KOIDE, “Sixth OLSR (Optimized Link State Routing) protocol,” and Toshio KOIDE, “Seventh AODV (Ad hoc On-demand Distance Vector) protocol.”
However, with the conventional method of deciding transmission paths, all the devices included in a network are possibly involved in a transmission path. That causes not only the access point devices but also the wireless network devices to be possibly involved in the transmission path.
For example, when a wireless network or mobile device moves, an access point device to be connected maybe replaced. If an access point is added or removed, then information on transmission paths may be updated accordingly. In addition to that, information on transmission paths for the wireless network devices provided at a distal end also has to be updated. That may cause transmission to be temporarily interrupted.
In general, a wireless mesh network is structured with either one of the two features: (a) each access point device forms a particular network separate in segment from others, and (b) a network formed between a wireless network device and an access point device is common to a network formed between access point devices.
However, with a network structured with the feature (a), when a wireless network or mobile device moves from one access point device interconnected thereto to a service area covered by another access point device, the wireless network device has to update data of the IP address stored to that of the other access point device, with the result that the network connection is interrupted and will not be available until a network connection is re-established.
On the other hand, in a network structured with the feature (b), plural networks co-exist each of which conveys a particular sort of communication different from each other in characteristics, such as speed of transmission or strength of the electrical field. Usually, efficient utilization of a certain network requires various parameters thereof to be tuned. Where plural sorts of networks co-exist as with the feature (b), the situation becomes more complex to the extent that it is difficult to select optimum parameters, thus deterring the efficient use of the network.
There is also raised a security-related problem that, communication between wireless network devices allows other, strange radio network devices to readily monitor transmission paths between the access point devices in the wireless network.
For these reasons, there has been raised a demand for a network switching system, in which communication may be carried out without being affected by settings of remote devices on communication between wireless network devices or between access points, and communication protocols or standards, aiming at preventing disconnection of transmission otherwise caused by updating transmission path information resultant from addition or removal of an access point device or movement of a wireless network device from one to another service area, and invasion into a transmission path from strange mobile devices, as well as achieving more efficient utilization of the network system.